Read the tax status page and the OSS counter

Choose Tax in the menu to open Tax status. It is read only and shows three cards: VAT return, OSS counter and Deadlines. It counts, warns and shows dates; nothing is filed or sent to ELSTER or the BZSt from here, the VAT return, the ZM and the OSS return are filed by a person. Everyone who can read the bookings sees the page.
VAT return shows the next return with its status (Open, Overdue or Locked, which means every month of that period is closed) and its due date. The dates are the statutory ones: a permanent extension is not recorded here. If the VAT return is switched off for the client, the card says so (see Set the VAT profile: small business, cash basis and return period). For a client outside Germany the card says the UStVA is not covered yet.
Deadlines lists every return of this calendar year with its status and due date (an annual filer has none). Below it the ZM line gives the number of lines of the last finished period, how many lack the buyer's VAT ID and how many carry a German VAT ID; it is filled in only once the VAT return is switched on (and not for an annual filer).
OSS counter adds up this calendar year's net sales to private customers in other EU countries against the 10,000 EUR threshold, with last year's amount, a bar and the sum By country (net). It shows two readings, Goods only and Goods plus all services, because only telecommunication, broadcasting and electronic services count towards the line and your tax advisor decides which of your services apply. It exists only for companies established in Germany.
What is counted: income bookings that are reviewed or posted, dated by their date of supply (otherwise the document date) in the year, whose customer is a private person in another EU country; a credit note reduces the sum. The card lists what it could not count: bookings without a customer, buyers without a country, bookings not yet reviewed or posted, and foreign-currency bookings without an EUR amount. Fix those bookings or contacts and the counter updates.
At 80 percent of the threshold the card warns you to check before the next sale to a private customer in another EU country. If the counter finds the threshold crossed, it says on which date and that the VAT of the buyer's country may apply from that delivery. The same goes for last year. These are hints, not tax advice: confirm with the tax advisor. Buyers to check names contacts in another EU country marked as a business without a foreign VAT ID. They are not counted, because a contact is a business by default and may really be a private person: choose Open contacts and clear Business customer (B2B) for a private person, or enter the VAT ID for a business.
For a small business the card adds that OSS usually does not apply. The OSS return itself is filed by hand in BZStOnline. At the bottom the page shows the client's Profit determination and Taxation basis; if they are not set, set them in Settings, Company profile.