Assets include things like the bank balance, invoices pending collection, or equipment; liabilities cover debts to suppliers, the tax agency, or the bank; equity holds the capital contributed plus accumulated results. For an SL, the balance sheet is part of the annual accounts filed each year with the Companies Register (Registro Mercantil).
Rather have this calculated for you?
kontora generates your tax forms box by box, tells you how much to set aside and reminds you before every deadline.