following number of documents

We have numbers 000001, 000002, 000003 and so on, and then input a document with number BB0001 (for example beginning balances). We want to have the next number 000004 again. If we adjust it manually, anyhow the system doesn't give the next number 000005 but BB0002. Is there any solution of this problem?

I'm sorry for my English: You can manually rename number "BB0001" of document in namber "000005", and the system "1C" create number "000006" for next new document. If you use any prefix ("BB" or any other), then the system create next new number used your prefix.

That's the problem. Normal numeration is increasing (000001, 000002, 000003 and so on). But if a user forgot some beginning balances and need to input one more invoice with the number "before", he/she will get a trouble. Moreover, usually in simple cases the first number in year is 000001. In our case beginning balances already reserve these first numbers. Is there any solution?

By the way: my English is also not so perfect  

You should enter beginning balances with the last date of previous year (31.12.XXXX)

It sounds logically (with previous year), but for example in 1C: Accounting Suite even if I input beginning balances with the date 31.12.XXXX I still get first numbers in the following year. Could you please check? I tested it many times, but get the same result.

There is no numbering adjustments in General ledger (Accounting register). You could create a separate document to add General ledger records and separate document for Beginning balances. Or you can use just one.

Document object permits set numbers unique within a year.

The other way is to use prefix "BB" and "00".

SetNewNumber("BB");
SetNewNumber("00");

It's common practice to use separate kind of documents for entering beginning balances and for everyday workflow.

It's also rather common for a user to change document number manually for some reason, though it is not recommended to. In this case, to retain document numbering, you may use OnSetNewNumber Event Subscription. There you can filter out wrong numbers, e.g. containing prefixes "BB", in your case, and calculate next number from what is rest. Just bear in mind possible number overflow.

@ mike_a: it's not common practice to use separate documents. Here in 1C: Accounting Suite is the same document with choice of boolean 'BegBal'. It is an idea of developers and not mine. So, how should it work?

Strange...In russian versions they do use separate documents. Though it's possible to enter beginning balances by ordinary documents in some cases.
Anyhow, you may try OnSetNewNumber Event Subscription.