MB-800 common mistakes
MB-800 · Understand the traps and how to avoid them.
Puts inventory/COGS accounts or customer posting-group combinations into General Posting Setup, then cannot explain why a sales invoice hit the wrong account.
The three posting-setup pages (General Posting Setup, General Business Posting Setup, Inventory Posting Setup) all use the phrase 'posting group' and the exam describes scenarios in prose without naming the page, so candidates guess by account name instead of by the key pair that drives the lookup.
What to do instead
Memorise the key pair for each page: General Posting Setup = General Business Posting Group x General Product Posting Group (revenue, COGS, inventory adjustments on sales/purchase lines); General Business Posting Setup = General Business Posting Group x Customer/Vendor Posting Group (receivables, payables, service charges); Inventory Posting Setup = Location x Inventory Posting Group (inventory, WIP, variances). VAT Posting Setup = VAT Business x VAT Product Posting Group.
Assumes that Default Dimensions set on a customer, vendor or item will appear on every journal and document line, and is caught out when a line has no dimension or carries a different value.
Default dimensions arrive from several sources at once (master data, posting setup, G/L account) and Business Central resolves conflicts using dimension priority rather than a simple 'last one wins'; candidates also forget that dimension combinations can block or force values.
What to do instead
Learn the Value Posting options on the Default Dimensions page (blank, Code Mandatory, Same Code), the dimension priority that resolves conflicting defaults, and the Dimension Combinations page that blocks invalid pairs. Remember only global dimensions are available for analysis views, and shortcut dimensions are configured separately.
After a year-end scenario the candidate tries to post a journal and gets a 'posting date is not within your range of allowed posting dates' error, then cannot locate the setting that is blocking it.
Posting-date restrictions exist in more than one place and they intersect: General Ledger Setup sets the overall range while User Setup can narrow it for the individual, and a new fiscal year must exist in Accounting Periods before anything can post into it.
What to do instead
Check User Setup first (it overrides/narrows General Ledger Setup), then the Allow Posting From / Allow Posting To fields in General Ledger Setup, and confirm the new fiscal year has been created on the Accounting Periods page. Note that only one accounting period can be marked as open for posting at a time.
Configures a customer-specific price and a line discount, then expects both to apply, or expects an invoice discount to be calculated per line.
Candidates treat pricing as one mechanism, but Business Central resolves the best (lowest) unit price and the best line discount independently per line through a defined source hierarchy, and invoice discount is a separate document-level calculation that must be enabled.
What to do instead
Know that the search goes from the most specific source (customer/item) outward to price groups and 'all customers', with quantity breaks and unit of measure considered. Line discounts require Allow Line Disc. on the customer; invoice discounts require Allow Invoice Disc. plus the Invoice Discount Calculation settings in Sales & Receivables Setup. Price Includes VAT is a separate flag on the price line.
Builds an approval workflow on the Workflows page, enables it, and then is surprised that sales orders post without approval or that the approval request cannot be sent.
Candidates think the workflow alone enforces approval, but the workflow must contain the correct response (Send Approval Request) and each approver needs an Approval User Setup record with an approval limit; without a matching approver the request stalls or the step is skipped.
What to do instead
Check three things: the workflow is enabled and the approval response is attached to the right event/condition, an Approval User Setup entry exists for the approver with the relevant sales/purchase approval amount limit, and the user has the permissions needed to send and approve requests. Remember the request is triggered from the document itself, not automatically on posting.
Posts purchase invoices with item charges or back-dated receipts and expects inventory value and COGS to be immediately correct, never running the cost adjustment.
Business Central values inventory asynchronously for several cost-affecting events; item charges, landed costs and back-dated entries need a batch job to propagate the cost into the affected item ledger entries.
What to do instead
Run Adjust Cost - Item Entries with an appropriate posting date after posting cost-changing transactions, and be able to explain how the item's Costing Method (FIFO, Average, Standard, Specific) changes the result. Standard-cost changes use the Standard Cost Worksheet rather than the adjustment job.
Applies a customer payment by typing the invoice number into Applies-to Doc. No. on a cash receipt journal line, or by manually setting an Applies-to ID, and leaves the invoice open after posting.
The Applies-to Doc. No. shortcut only closes the invoice when the payment amount matches exactly; otherwise the entries must be applied on the Customer Ledger Entries page, which is a step candidates skip before posting the journal.
What to do instead
Either use the Payment Reconciliation Journal / Cash Receipt journal with an exact-match Applies-to Doc. No., or assign an Applies-to ID and use Apply Entries on the customer ledger entries before posting. Always verify the outcome on the Customer Card or Customer Ledger Entries rather than trusting the journal screen.
Treats the Bank Account Reconciliation page as something that posts the whole statement, or cannot get the worksheet to balance because the bank account is not linked to a G/L account.
Candidates conflate the Bank Acc. Reconciliation worksheet (statement lines matched against ledger entries) with the Payment Reconciliation Journal (applying customer/vendor payments), and forget that a Bank Account Posting Group is what links the bank account card to the G/L bank account.
What to do instead
Set up the Bank Account Posting Group on the bank account card so the account maps to a G/L bank account, then match statement lines to existing ledger entries or create new lines for charges/interest; only those created lines post. The reconciliation is finished when the Difference is zero. Use the Payment Reconciliation Journal when the task is applying customer payments, not reconciling the statement.
Assigns a permission set, edits it, and expects the change to take effect immediately; or grants SUPER to make a problem go away.
Permissions are evaluated per session and some permission sets depend on indirect (Execute) permissions granted elsewhere, and the UI often hides actions instead of raising an error, so the candidate misdiagnoses the cause.
What to do instead
Verify the result on the Effective Permissions page and sign out and back in after changes. Remember that permission sets can require indirect permissions and that record-level access is controlled with security filters. Use targeted permission sets rather than SUPER so the exam scenario's least-privilege requirement is satisfied.
Assigns the customer, vendor or item number series on General Ledger Setup, or reuses a series after copying a company, and then gets blank numbers or 'number already exists' errors.
Number series are assigned on the setup page of the area that owns the record (Sales & Receivables Setup, Purchasing Setup, Inventory Setup, General Ledger Setup), and No. Series Lines hold the last-used date and number, which goes stale when data is copied or restored.
What to do instead
Map each record type to its own setup page and configure Default Nos. and Manual Nos. deliberately, using No. Series Relationships where a series must share one sequence. Repair gaps or duplicates on the No. Series Lines page by correcting the Last Used Date/No., not by creating an unrelated new series.